This invention relates to a device called a xe2x80x9clurexe2x80x9d, that allows treatment of a substrate in a machine provided for the treatment of bigger substrates and a mounting system for a substrate in this device.
It is applied notably in the field of micro-electronics, in the case of the treatment of semiconductor substrates, for example silicon wafers, or ceramic substrates which are, for example, intended for the manufacture of hyper-frequency devices.
The machines intended for the treatment of silicon wafers are provided to treat wafers, the diameters of which are chosen from among a limited number of diameters or to treat wafers of a single diameter. When one wishes to treat wafers having a diameter less than this diameter, the machines must be modified.
It is also known to manufacture lures (FIGS. 1A to 1D). To do this (FIG. 1A), a silicon wafer 2 having a diameter less than that accepted by a treatment machine can be fixed by means of a layer of adhesive 4 onto another silicon wafer 6 having the diameter that is accepted by the machine. However, out-gassing from the adhesive contaminates the machine.
It is also known to position the wafer 2 in a cutout with an open bottom, formed in a silicon wafer 8 having the diameter accepted by the machine (see FIG. 1B). However, this poses the problem of transporting the lure obtained in this way since the wafer 2 is not held in the cutout. Because of this moreover, it risks being ejected when a plasma is formed in the machine. It is also known (FIG. 1C) to hold the wafer in a stack of two rings 10 and 12 locked one against the other by screws 14, each ring having an external diameter equal to that which is accepted by the machine. However this solution has disadvantages: the stack of rings 10 and 12 and the immobilization of the wafer 2 within them is too difficult to obtain. The wafer risks being scratched and there is a risk of particulate contamination. Furthermore, if the ring 10 is not sufficiently cooled, it can burn the resins painted on the wafer.
It is also known to hold the wafer 2 in a stack of two rings 16 and 18 (FIG. 1D) which are not fixed one to the other and whose external diameter is still equal to the diameter accepted by the machine, the bottom of the lower ring 18 being closed but being provided with small holes 20 that permit passage of a treatment gas. However, this solution has the disadvantage of requiring an upper ring 16 having a weight that is sufficient to prevent the ejection of the wafer 2 during treatment of it by a plasma, which leads to an assembly that is too heavy.
Furthermore, the pressure of the heat-exchange gas (for example helium) generates pressures that correspond to the application of a force of the order of 10N on a wafer of 100 mm diameter. The weight of the ring 16 would therefore have to be greater than this value.
The purpose of this invention is to remedy the preceding disadvantages.
First of all the subject of the invention is a device that allows the treatment of a first, substantially circular substrate, having a first diameter, in a machine provided for the treatment of substrates that are substantially circular, having a second diameter, greater than the first diameter, this device being characterized in that it comprises a ring capable of setting the first substrate, this ring being made of a material which is compatible with the treatments to be carried out in the machine and having an external diameter equal to the second diameter, and an internal diameter less than the first diameter, this ring being capable of expanding sufficiently by heating, or the first substrate being capable of contracting sufficiently by cooling, with the idea of setting this first substrate in the ring.
Preferably, when the first substrate is a semiconductor or ceramic substrate, the ring is capable of expanding sufficiently by heating for such setting to occur.
When the first substrate is a silicon substrate, an anodized aluminum ring or an aluminum ring coated with a layer of protective resin can be used.
According to a preferred embodiment of the device which is a subject of the invention, the ring includes an internal flange capable of holding the first substrate during its treatment in the machine.
Also preferably, in order for the stresses that are liable to be applied to be as weak as possible, the ring includes a cutout formed along the entire length of the internal wall of the ring, which has a shape that is substantially complementary to that of the edge of the first substrate, with a view to it receiving the latter.
For reasons of simplicity of manufacture, in place of such a cutout, it is preferable that the ring includes a cutout formed along the entire length of the internal wall such that when this internal wall is viewed in transverse section, it has the shape of an acute angle, one side of which is perpendicular to the A axis of the ring and which has a value that is sufficiently large to receive the edge of the first substrate.
Preferably this acute angle has a value of approximately 60xc2x0.
This invention also relates to a system of mounting the first substrate in the device that is a subject of the invention, characterized in that it comprises:
manipulation means provided to put the first substrate into place in the ring and to move this first substrate when it has been set in this ring and
means of heating the ring or of cooling the first substrate so as to be able to set this first substrate in the ring.
In the case where the first substrate is a semiconductor or ceramic substrate, preferably, as has been seen above, a ring is used that is capable of expanding sufficiently on heating for the setting operation to occur. In this case, the system includes means of heating the ring so as to be able to set this first substrate in the ring. These heating means can comprise a retractable crown having an external diameter at least equal to that of the ring and an internal diameter that is greater than the diameter of the first substrate, this crown incorporating resistance heaters. As a complement to the heating means, means intended to cool the ring when the first substrate has been put into place may also be provided.